1. Field of the Invention
The present invention generally relates to a touchscreen, and more particularly, to a touchscreen with a mesh-like electrode pattern which is capable of eliminating the moiré phenomenon.
2. Description of the Prior Art
Touchscreen displays are able to detect a touch within the active or display area, such as detecting whether a finger is present pressing a fixed-image touchscreen button or detecting the presence and position of a finger on a larger touchscreen display. Some touchscreens can also detect the presence of elements other than a finger, such as a stylus used to generate a digital signature, select objects, or perform other functions on a touchscreen display.
The Use of a touchscreen as part of a display allows an electronic device to change a display image, and to present different buttons, images, or other regions that can be selected, manipulated, or actuated by touch. Touchscreens can therefore provide an effective user interface for cell phones, GPS devices, personal digital assistants (PDAs), computers, ATM machines, and other devices.
Touchscreens use various technologies to sense touch from a finger or stylus, such as resistive, capacitive, infrared, and surface acoustic sensors. A capacitive touch screen, for example, may include an insulator coated with a transparent conductor such as indium tin oxide (ITO) or transparent conductive polymers such as PEDOT (polyethylene dioxythiophene) in a particular pattern. When an object, such as a finger or a stylus, touches the surface of the screen, there may be a change in capacitance. This change in capacitance may be sent to a controller for processing to determine where the touch occurred on the touch screen.
While transparent conductors such as ITO may be used for electrodes, however, since the transparent conductive layer has high resistance of 100 ohms/square or more, the sensitivity is lowered when the display device is manufactured in a large scale, and as the size of screen is increased, the cost of the ITO film is rapidly increased. Accordingly, it is not easy to perform commercialization thereof.
In order to overcome this conventional issue, there is an effort to implement enlargement by using an opaque metal pattern having high conductivity. When the electrode pattern is made of the metal, electric conductivity is excellent, and demand and supply is smooth. In the case in which the electrode pattern is made of the metal such as copper, silver or other conductive materials, the electrode pattern should be formed in a mesh structure in a micrometer (μm) unit in order to prevent users from recognizing the electrode pattern and make the electrodes substantially invisible to the naked eye.
However, when the electrode pattern of the touch panel is formed in the mesh structure having regular and constant intervals, there is a problem in that period characteristics of the metal mesh electrode pattern of the touch panel may cause interference with a periodic pixel pattern of the IC circuit or a regular pattern structure of another optical film, such as a black matrix pattern of a color filter included in an image display device overlapped with each other, thereby causing a so-called “moiré” phenomenon. Herein, the moiré means an interference pattern formed when two or more regular and repeating patterns overlap.
The occurrence of moiré makes it difficult to see a displayed image of the display, and thereby deteriorates the visual operability or usability of the touch screen device. Categorized broadly, moiré may be low-frequency moiré in which large patterns consecutively appear, or high-frequency moiré in which small patterns consecutively appear. In particular, low-frequency moiré will make the display difficult to be viewed.